Aerosols are gaseous suspensions of fine solid or liquid particles. Aerosols are useful in a wide variety of applications. For example, medicated liquids may be administered in aerosol form. Medicated aerosols include materials that are useful in the treatment of respiratory ailments. In such applications, the aerosols may be produced by an aerosol generator and inhaled into a patient's lungs. Aerosols are also used in non-medicinal applications including, for example, dispensing air fresheners and insecticides and delivering paints and lubricants.
Aerosol generators are known that include a heated tube for vaporizing liquid. For example, commonly assigned U.S. Pat. No. 5,743,251, which is incorporated herein by reference in its entirety, discloses an aerosol generator including a tube and a heater operable to heat the tube to a sufficient temperature to volatilize liquid in the tube. The volatilized material expands out of an end of the tube and admixes with ambient air, thereby forming an aerosol.
As shown in FIG. 1, an aerosol generator 21 disclosed in U.S. Pat. No. 5,743,251 includes a tube 23 defining a capillary sized fluid passage and having an open end 25. A heater 27 is positioned adjacent to the tube 23. The heater 27 is connected to a power supply 29. The tube 23 also includes an inlet end 31 in fluid communication with a source 33 of liquid material. In operation, liquid is introduced into the tube 23. The heater 27 heats a portion of the tube 23 to a sufficiently high temperature to volatilize the liquid. The volatilized material expands out of the open end 25 of the tube. The volatilized material admixes with ambient air and condenses to form a condensation aerosol.
Other exemplary aerosol generators including a heated tube for vaporizing liquids to produce a condensation aerosol are disclosed in commonly assigned U.S. patent application Ser. No. 09/956,966 filed Sep. 21, 2001 and Ser. No. 10/003,437 filed Dec. 6, 2001, and in commonly assigned U.S. Pat. No. 6,234,167, the disclosure of each being incorporated herein by reference in its entirety.